Boiler return pump

Patk · October 2022

Image: https://us.v-cdn.net/5021738/uploads/editor/k4/1lo5e365oa8x.jpg

Hi, i have a 2 pipe steam boiler in an old Firehouse I'm fixing up There is a tank and pump that brings water back to the boiler. How long after the boiler shuts down should this pump run? Thanks!
BTW the water you see is from a leaky basement and not a leaky boiler.

Snowmelt · October 2022

Good question, I serviced an art school that had a gym with boiler on one side and the condensation pump on other side, maybe 20 to 40 seconds 30 being the happy medium. It would go off every 5 -10 minutes

pedmec · October 2022

Depends on how much water the boiler needs, size of the pump, and type of control. It's not a one size fits all.

Also in a properly operating system the boiler should not shutdown waiting for condensate pump to replenish the boiler. The condensate pump should kick on before the boiler cuts out due to low water.

Jamie Hall · October 2022

Can't really put a number on that. It should run just long enough to bring the water level in the boiler to the normal level. More to the point, it should be controlled by the water level in the boiler -- allowing it to drop some when running (but not to the low level water cutoff) and then restoring it to no more than the cold level. It should NOT be controlled by the level in the tank! That level, however, should be what controls when (and if) makeup water is added.

Pumpguy · October 2022

This is a simple condensate return pump, operating start - stop controlled by the float switch.

It isn't wired to and doesn't care about how much water is in the boiler or what the boiler needs.

The pump will run start - stop so long as condensate is flowing into it. Think of a basement sump pump. Same principle.

If you have a problem with the boiler needing to take on feed water from the low water make up, or being flooded with too much water, there are other problems that need to be addressed.

If these are the case, give us more detail and we'll see what we can come up with.

mattmia2 · October 2022

You probably want to flush the returns to make sure they are clear. If water keeps dribbling in because the returns are clogged it could cycle for a long time after the boiler stops.

ScottSecor · October 2022

I'm not sure this is a simple condensate unit. If you look closely at the photo there is a green what appears to be a solenoid valve.

Most condensate tanks we see work off of a "dumb" float valve and turn on when full (realistically about half full). Much like a sump pump in a pit.

Most boiler feed tanks we see are turned on and off through a "smart" float control, typically as part of a low water cutoff. Most, if not all boiler feed tanks also have a built in water feeder.

Both condensate tanks and boiler feed tanks are sized on boiler output and lag time (how long does it take to get the system condensate back to the tank).

These two links may help.

pedmec · October 2022

in my experience i've never seen a condensate pump with a solenoid operated water level control valve. only boiler feed tanks have water level control valve so the pump don't run dry. although it does look like a condensate pump but the water level control is what sets it apart.

JUGHNE · October 2022

Is there a cold fresh water line connected to the pump or is the water line connected to the boiler with some form of auto fill for the boiler?

Pumpguy · October 2022

In lieu of mechanical make up float valves on boiler feed pump receiver tanks, float switch and solenoid valve arrangements are often used instead.

I too am wondering what that green doo-dad is fitted to the top of the pump's receiver tank. Fitted to the top of the tank, I don't see how it could trigger low water make up, and where would the low water make up come from? Doesn't look like any float switch I've ever seen. Probes maybe? Too bad that flex conduit obstructs most of the view.

I'm also wondering what that green corroded brass colored item is, and the large blue thing just above. Are these related to the return line and boiler operation in any way?

All this said, I'm pretty sure this is a common float switch operated condensate return pump.

Hopefully @Patk will answer back and we can get some answers.

Steamhead · October 2022

That solenoid valve probably worked off the boiler's low-water cutoff. Instead of a dedicated feed valve going into the return at the boiler, it discharged into the pump's reservoir, and the water was pumped back to the boiler. I once ran into an Iron Fireman SelectTemp system that was set up this way.

Pumpguy · October 2022

Steamhead said:
That solenoid valve probably worked off the boiler's low-water cutoff. Instead of a dedicated feed valve going into the return at the boiler, it discharged into the pump's reservoir, and the water was pumped back to the boiler. I once ran into an Iron Fireman SelectTemp system that was set up this way.

I see. Yes, that would make sense.

Boiler return pump

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